A guide block for an MRI device has a block body with a proximal face, a distal face, and a plurality of passageways extending between the two faces. A first guide passageway within the guide block is open along the body length, extends between the proximal face and the distal face, and is configured to receive a tissue-removing device. A second guide passageway within the guide block is open along the body length, extends between the proximal face and the distal face, and is configured to receive the tissue-removing device. A longitudinal opening extends between the first guide passageway and the second guide passageway, and is coextensive with the first guide passageway and the second guide passageway between the proximal face and the distal face.
